This invention relates to a multiple-speed transmission for motor vehicles having one main transmission and one range change group of planetary design rear-mounted thereon and having a synchronizer unit situated on the output shaft of the main transmission which, at the same time, is the input shaft of the range change group.
Multiple-speed transmission for industrial vehicles cannot be built with adjacently disposed gear pairs, since one such known transmission made so long has a strong bending of the shaft under load and a poor contact pattern of the gears. Therefore, with more than six gears the transmissions are usually designed in multi-group construction, i.e. to the main transmission is attached a front-mounted or rear-mounted group which can also be integrated in the main transmission. A differentiation has to be made here between a split and a range change group.
The split group doubles the number of gears, i.e. in a four-gear counter-shaft transmission as a main transmission, the ratio range in the center is halved. This results in eight fine gear gradations in the total range of ratios.
The range change group is rear-mounted, short, one-step planetary transmission which, nevertheless, does not concentrate but lengthens the gear sequence. This means that the first gear step of the range change group to be engaged attaches itself to the directly driving step of the last step of the main transmission. This is obtained by the speed ratio change of the range change group being higher than the total ratio change in the main transmission. Combined with a front-mounted split group and a main transmission, a transmission with sixteen gears can thus be implemented. Such a transmission satisfies all requirements the same as the economical use of heavy industrial vehicles in street traffic. The already known multiple group transmissions of this design have a high mechanical, total ratio of about 10 to 17.5.
DE-A 31 29 414 has disclosed a planetary wheels reversing transmission for a continuously adjustable, traction roller transmission of a motor vehicle having a planetary wheel transmission disposed coaxially relative to the input shaft and to the primary shaft of the traction roller transmission, which surrounds it as hollow shaft and having its input element connected with the input shaft and its output element with the primary shaft. Two additional components for shifting a forward and a reverse gear range can be fastened by a brake or by a clutch, an idle or neutral range being shifted when the devices are loosened. In a planet gear carrier provided as input element and having two intermeshed planetary gear sets of which, one is meshed with the sun gear provided as an output element and the other with the ring gear provided as a reaction element, the ring gear is used in its periphery as synchronizer hub for a synchronizer sleeve which, on one side, interacts via a synchronizer ring with a synchronizer taper ring non-rotatably fasted on the transmission cover or via a synchronizer ring with a synchronizer taper disc built on the planet gear carrier.
This known transmission has a small installation space and a low construction cost for its control; the hollow gear serves, in addition, as a clutch carrier with the interacting synchronizer taper segment and the shift sleeve, wherein it is laterally settled as a disc part and axially retained by means of two thrust washers against the web and transmission cover. This known transmission has an upper synchronous assembly position with an axially fixed ring gear, a reduction of shift jerks being obtained by intercalated synchronizer rings.
EP-PS 239 555 has disclosed a planetary transmission having an axially movable ring gear, which is also designed as a sliding sleeve and has, on the ends, meshing teeth which converge toward inner teeth which mesh with the planetary gears. The meshing teeth interact in an axial direction with a clutch body, the synchronizer rings are provided with outer locking teeth and friction surfaces which grind as tapered segments on the clutch body. By means of a spring device, outer teeth of the synchronizer rings are under spring tension against the outer gearing of the synchronizer ring. Thereby resulting in an angular play of tooth width in the tangential direction. The spring device in the inner gearing of the ring gear produces an abutting position of the synchronizer rings, i.e. an angular movement relative to the ring gear. To obtain a compact design, an upper synchronous assembly position is provided, wherein the ring gear is axially movable and drafted as a shift sleeve while the locking takes place via tangentially disposed spring devices in the ring gear.
EP-PS 423 863 finally describes a transmission in which an axially movable ring gear is, at the same time, designed as a sliding sleeve, thus, ends having on the inner gearing, meshing teeth, which converge toward inner teeth which mesh with the planetary gears. The meshing teeth can mesh in an axial direction with the clutch body; synchronizer rings with outer locking teeth and friction surfaces which grind as tapered segments on the clutch body are provided with outer bolts. The outer gearing of the synchronizer ring presses, via a spring device upon a bolt; an the angular play, in the tangential direction of the synchronizer ring, amounts to the width of a tooth.
A spring device lies in recesses on the axial ends of the ring gear, the locking body pressing upon the synchronizer ring from outside. Here is also obtained a compact design by an upper synchronous assembly position with axially movable ring gear drawn up as a shift sleeve. Likewise, the locking takes place via radially disposed spring devices in the ring gear.
The problem on which this invention is based is to provide a multiple-speed transmission for motor vehicles having a main transmission and rear-mounted thereon a range change group of planetary design, wherein the range change group has a one-step planet drive with a high ratio, the two gears of which can be shifted by means of a synchronizer unit and which makes possible a short shifting time, a quick unlocking, extensively reduced grinding, considerably less meshing hindrances and elimination of transmission noises.